Fire resistant cellulose insulation and method of production from sugar cane bagasse

ABSTRACT

The present invention is a fire resistant cellulose insulation material made from agricultural byproduct containing cellulose fiber, comprising:  
     cellulose fibers that have been bathed in an effective amount of a first aqueous solution of chemicals suitable for separating and partially dissolving said cellulose fibers, followed by an effective amount of a second aqueous solution of chemicals suitable to neutralize said first aqueous solution, and  
     a fire retardant chemical produced from the neutralization of said first aqueous solution by said second aqueous solution, said fire retardant chemical precipitated on said cellulose fibers. A method for making same is also disclosed and claimed.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to the insulation materialsprocessed with fire retardant chemicals, which are widely used in theconstruction industry, specifically, fire-resistant cellulose materials.Building insulation materials are needed to increase thermalperformance, while satisfying constraints such as durability, cost,dimensional limits, and environmental, safety, and health concerns.Building insulation materials are used to improve energy savings, fireresistance, sound proofing, and comfort. They are manufactured frommineral fibers, fiberglass, plastic foam, and cellulose materials.Fiberglass insulation is the most widely used residential and commercialbuildings in the developed world. Today, this product is coming underscrutiny. Some concerns have been raised regarding the harm frominhaling airborne dispersed fiberglass, which has been found to bepotentially carcinogenic.

[0002] The second most used insulation product is one that ispolyurethane-based. Today, it is well known that human exposure toisocyanate, benzene, and methylene chloride at polyurethane foammanufacturing plants increases the risk of developing cancer; sufferingadverse effects on the heart, central nervous system, and liver;irritating the skin, eyes, respiratory system; and acquiring chemicalpneumonia.

[0003] Several studies have concluded that cellulose insulation is theleast polluting material and the healthiest. Cellulose insulationproduction consumes about 20-40 times less energy than mineral fiberinsulation materials. More importantly, cellulose has a thermalconductivity of approximately 0.026 W/m°K, while standard fiberglass has0.040 W/m°K. This means that cellulose has a 35-38% larger R-value thanfiberglass with same thickness, which translates to better insulationproperties.

[0004] Several methods exist to produce cellulose pulp, but most areintended for paper, textile, and plastic production because they arecurrently more profitable businesses than insulation production. Thesesame methods would be extremely expensive for producing buildinginsulation material. Thus, building cellulose insulation is producedfrom recycled materials instead of from cellulose pulp. Currently, only7% of building insulation materials is produced from cellulose. Rawmaterials used for producing cellulose insulation may range fromrecycled newspaper, paperboard, and cardboard. These materials areprocessed to manufacture a finely divided material with a very low-bulkdensity.

[0005] To improve the fire-resistant properties of the paper basedcellulose material during production, the raw materials are treated withfire retardant substances that are traditionally applied in powder orliquid solution forms to be impregnated to the cellulose material.

[0006] Over one hundred patents for producing cellulose insulation fromnewspapers have been issued since 1949. Some of the fire retardantsubstances used include ammonium phosphates, ammonium sulfates,carbonates, boric acid, sodium tetra-borate and mixtures thereof. Forexample, cellulose insulation materials and fire retardant substancesare discussed in U.S. Pat. Nos. 4,168,175, 4,224,169, 4,342,669,4,349,413, 4,595,414, 5,455,065, and 5,534,301. These methods improvethe properties of the recycled paper, but do not address the need forcellulose material with intrinsic properties necessary for advancedinsulation materials as it is disclosed in the present invention, wherethe intrinsic properties of the cellulose material are enhanced at themolecular level to satisfy a more advanced behavior of the material andinsulated system. On the other hand, current cellulose insulation ismanufactured from recycled newspapers, which means that the cellulosematerial contains a 5-10% by weight of ink, which is alwaysformaldehyde-based ink. The formaldehyde-based ink increases the thermalconductivity of the material and decreases its corollary: the thermalconstant R. In addition, the formaldehyde content reduces the healthcharacteristics of any building insulation material. The inventiondisclosed in the present document is based on an innovative method,which gives the possibility to produce modified cellulose with advancedproperties and characteristics, as needed for insulation materialapplications.

[0007] The increment of the cellulose production is well based accordingto the functionality of this material; however, the increase of theproduction of the cellulose materials is limited by the availability ofthe paper residuals since the paper production is the major consumer ofthis raw material. According to “The Recycler's Handbook,” “a ton ofpaper made from 100% wastepaper, instead of virgin fiber, saves 17trees, 7,000 gallons of water and 60 pounds of air-polluting effluents,4100 kwh of energy, three cubic yards of landfill space and taxpayerdollars, which would otherwise be used for waste-disposal costs.” Incontrast, using recycled paper to produce insulation material is neitherthe most economical nor the best environmental solution.

[0008] The present invention gives a solution for producing buildingcellulose insulation material from agricultural waste and/oragricultural byproducts such as, in a preferred embodiment, sugar canebagasse, which is the fiber component of the sugar cane stalk remainingafter the extraction of sugar cane juice. Byproducts that can be usedfor the production of fire resistant cellulose material includesugarcane bagasse, guayule bagasse, and other vegetative residuals fromthe extractive processes of oils, resins, wax, and aromatic components.The invention is based on an innovative process that separates thecellulose fibers from the bagasse material and simultaneously treatsthem chemically to add the fire-retardant characteristics to produce alow cost and environmentally safe insulation material.

[0009] The basis of the present invention is a closed process or methodthat integrates all major processes for pulp production. This process ormethod was developed not to produce pulp, but instead, to separate andstabilize the cellulose fibers using chemicals, which later areneutralized to form the fire-retardant and fungi-resistant compounds.These compounds are molecularly precipitated over the elemental surfaceof the cellulose structures that have been partly dissolved by theprocess, thus acting more efficiently, diminishing its corrosiveness,and remaining in the cellulose material to add fire-retardantcharacteristics. Consequently, this method will generate very littlewaste, if any.

[0010] This method serves as an option to stop or diminish theutilization of harmful insulation materials. This method serves to reusea wide group of agricultural byproducts, and agricultural wastes, whichalter the ecological equilibrium at the disposal regions. This methodserves to produce modified cellulose, specially designed to haveincreased thermal performance and improved functional characteristics,while decreasing environmental, safety, and health risks.

[0011] A preferred embodiment of the method uses sugar cane bagasse,which is the fiber component of the sugar cane stalk remaining after theextraction of the sugar cane juice. Byproducts that can be used for theproduction of fire resistant cellulose material include sugarcanebagasse, guayule bagasse, and other vegetative residuals from theextractive processes of oils, resins, wax, and aromatic components. Thepresent innovation represents an important advance in the state of artof cellulose insulation materials, giving a formulation and benignprocess for producing thermal insulation.

BRIEF SUMMARY OF THE INVENTION

[0012] The present invention provides a method for producing a low costinsulation from cheapest raw material, by using a minimal amount ofprocess steps and production machinery, conforming a low costtechnology-manufacture process. It provides a method for producing afire resistant cellulose insulation product, which is characterized by ahigh degree of safety with minimal environmental impact, and which meetsall applicable government regulations. The method produces a fireresistant cellulose insulation product that is characterized by a lowbulk density, high degree of fiber rigidity, stability, non-toxic, soundproofing, high R value, and fungi resistance.

[0013] These benefits are achieved through the exclusive use of theinnovative system/process for simultaneous separation of the cellulosefibers and formation of the insulation material from agricultural byproducts such as, in one embodiment, sugar cane bagasse, comprising thefollowing steps: mixing the washed bagasse particles with milled paperand cardboard residuals in a primary aqueous solution of chemicals tofacilitate the separation and preservation of the cellulose fibers, andneutralizing the mixture in a secondary aqueous solution to generatemodified cellulose and produce and precipitate over the fibers thefire-retardant and fungi-resistant compounds.

[0014] The neutralized mixture can then be compressed and strained toform insulation board panels, insulation compressed cakes or desired endforms of insulation material.

[0015] This invention provides a method for producing a fire resistantcellulose insulation material using a minimal amount of process stepsand production machinery conforming a low cost technology/manufactureprocess. This technology does not have byproducts or rejected productsand offers a method to separate the cellulose fibers from bagasse andsimultaneously treats them chemically to add the fire-retardantcharacteristics generating very small residuals. Moreover, the chemicalprocesses traditionally calculated for the reactors, in the presentinvention take place on the system of reactor-conveyers giving a higheconomic effect. The claimed method serves as an example having highecological significance. This method does not generate residuals andworks as an option to stop the incineration of the bagasse, whichcontaminates the environment. Finally, the present invention representsan advance in the art of cellulose insulation manufacture, and providesmany economic, safety, quality control, and other benefits compared withthe previous reported technology and cellulose materials, as discussedbelow.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0016]FIG. 1 is a schematic illustration of the process steps,materials, and procedure associated with the production of fireresistant cellulose insulation products from bagasse, in accordance withthe preferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017]FIG. 1 involves a schematic illustration of the process steps, rawmaterials, and equipment, which are used in accordance with a preferredembodiment of the invention.

[0018] The system in a preferred embodiment, has the followingcomponents:

[0019] 1. Cutter mill, to reduce the bagasse that all of the particlesthereof are capable of passing through a sieve within 15-20 mm ofdiameter.

[0020] 2. Bath-I, to wash the reduced material from the remnant sugarand lignin.

[0021] 3. System to add and control the used chemicals to theoperational Baths.

[0022] 4. Conveyer, special designed as described in FIG. 2.

[0023] 5. Hammer mill, to reduce the paper and cardboard residuals thatall of the particles thereof are capable of passing trough a sievewithin 5×5 mm. According to the present invention, othercellulose-containing materials can be incorporated to the residuals, andthe type of mill and sieve can be varied depending on needs.

[0024] 6. Bath-II, to mix the reduced bagasse and paper particles inaqueous solution, and chemically treat the mixture to accelerate thecellulose separation process and partial dissolution.

[0025] 7. Conveyer, analogue to (4).

[0026] 8. Bath-II, to neutralize the mixture, produces, and precipitatesthe fire-retardant and fungi-resistant components on the surface of thecellulose material.

[0027] 9. Conveyer, analogue to (4).

[0028] 10. Water recycling system.

[0029] 11. Filter-press, to partially dry the material. Two systems worktogether in parallel: the first, to perform the insulation panels, andthe second, to perform cakes.

[0030] 12. Conveyer to transport the panels and/or compressed cakes. Thepanels and cakes are transported on the conveyer into dryer.

[0031] 13. Dryer. This is a tunnel kill calculated to work with electroenergy and/or sun energy, depending on the weather conditions.

[0032] 14. Hammer mill, to reduce the dried material to a disperse statefor blowing application. For this application in the press-filter werepreviously prepared the insulation cakes.

[0033] 15. Conveyor to transport the pulverized material to the desiredpackaging device.

[0034] 16. One or more packaging machines.

[0035] The Baths are specially designed to satisfy the technologicalexigency of the present invention. The Baths are equipped withtemperature control, agitation, peristaltic pump and filtration devices.They are connected to the water recycling station, and to the system forchemical control. The dryer is a phenomenal ecological installationcalculated to have permanent heat airflow for removing the humidity ofthe material. For the cloudy days, the solar installation is equippedwith air extractor, ventilator and electrical heating to be useoptionally.

[0036]FIG. 2 is a schematic illustration of the environmentally benignsystem for producing insulation material comprising a reactor-conveyorsystem build with baths and conveyers with progressive cavity screw forcontinuous mechanical, thermo-mechanical and chemical treatment of thecellulose:

[0037] 1. Bath-I, to wash the reduced material from the remnant sugarand lignin. The described process only produces small residues in thisstep. The produced solution is recycled in a parallel station.

[0038] 2. Bath-I, to mix the reduced bagasse and paper particles inaqueous solution and treat the mixture chemically to facilitate thecellulose fiber separation, partial dissolution, and conservation.

[0039] 3. Bath-II, to neutralize the cellulose mixture and precipitatethe fire-retardant and fungi-resistant compounds.

[0040] The baths are connected between them trough the conveyers. Theconveyors are enclosed and have an Archimede's screw or progressivecavity screw to transport and separate the cellulose fibers. The bathsand conveyers are designed for the thermo mechanical and chemicaltreatment. The conveyers are built to be able to recycle and reuse thechemical solution, and to facilitate the continuous process during thetransportation of the material from one technological step to another.By this procedure the cost of the processes are reduced.

[0041] All concentration percentages described below refer to percent byweight of overall mixture. With reference to FIG. 1, the bagasse ismilled (1) that all of the particles thereof are capable of passingthrough a sieve within 15-20 mm of diameter. Later, the material istransported to the Bath-I (2), where the material is washed. In Bath-I,the thermo-mechanical treatment is performed at 50-70 Celsius degrees.The amount of the bagasse particles oscillates between about 20% andabout 25% of the water. After strong agitation, the reduced bagasseparticles are more dispersed and the lignin and sugars are separated asbyproducts. The separated cellulose fibers are to Bath-II (6) on aconveyor (4). The conveyor is enclosed and has an Archimede's screw orprogressive cavity screw that continue separating the cellulose fibers.The screw continue grinding the fibers and separating the cellulose. Thelignin liquor is recuperated and returned back to the Bath-I to continuewashing the bagasse. Periodically, the liquor is removed to the waterstation (10) for recycling or used for production in parallel station.Chemical treatment will take place in Bath-II to complete the separationof the cellulose fibers. Different chemicals can be used depending ofthe processing history of the bagasse used for producing insulationmaterial, also depending of the most appropriate fire-retardantcomponent to be produced.

[0042] Preferred Chemicals

[0043] Table 1 below shows examples of the chemical substances used tofacilitate the separation of the cellulose and corresponding group ofsubstances for neutralization that can be used to produce thefire-retardant components. TABLE 1 Chemical substance for celluloseChemical substance Resulting fire- Example separation for neutralizationretardant agent 1 Sodium hydroxide Boric acid Sodium borate salts 2Sodium carbonate Boric acid Sodium borate salts 3 Aluminum Sulfuric acidAluminum sulfate hydroxide 4 Sulfuric acid Aluminum Aluminum sulfatehydroxide 5 Sulfuric acid Ammonia Ammonium compound sulfates 6Phosphoric acid Ammonia Ammonium compound phosphates

[0044] To facilitate the explanation of the preferred embodiments of thepresent invention, hereto is described the caustic treatment andneutralization with boric acid solution. However the scope of thepresent invention is not limited to the described example and wasdeveloped for the caustic and acid types of cellulose treatment, as wellas for the acid and basic neutralization processes.

[0045] Following the above declared, in Bath-II the treatment isperformed by using sodium hydroxide solution prepared at about 9% toabout 15% of normal concentration. Also, the hydroxide solution servesto prevent the possible decomposition of cellulose and hemicellulose ofthe bagasse and softens the material acting over the surface of thecellulose aggregates. In addition, in Bath-II the bagasse fibers aremixed with the finely divided particles of paper and cardboard. Thisrecycled paper material was previously milled into the hammer mill (5)and it is continuously transported to the Bath-II. The recycled paperand/or cardboard are added in about 10% to about 50% of the bagasseconcentration. In Bath-II the chemical substances are impregnated intothe cellulose fibers. The total weight of the cellulose mixture shouldnot exceed about 25% of the sodium solution to guarantee an efficientagitation process and sufficient impregnation. To facilitate the mixingprocess about 5% to about 8% of sodium carbonate was added to themixture. These chemicals facilitate the deflocculating process partiallydissolving the surface of the agglomerated cellulose fibers. Thus,chemicals will be added as needed by automated system (3) in order tokeep a constant concentration level in Bath-II.

[0046] After strong agitation, the mixture of dispersed cellulosematerials basically impregnated in sodium hydroxide and sodium carbonateis carried into Bath-II (8) for neutralization. The velocity of theconveyer (7) and its inclination angle is calculated to carry out anequivalent ratio of cellulose mixture and sodium solution (about ½ ofthe both substances).

[0047] In FIG. 2 is shown the reactor-conveyer system. Boric acidsolution is added to Bath-III (8) as need for the neutralizationprocess.

[0048] The following equations show the chemical reactions of thetreatment conducted in Bath-III to neutralize the caustic treated fibersand add fire-retardant compounds:

4H₂O+2Na(OH)+4H₃BO₃→Na₂B4O₇*10H₂O+H₂O.  (1)

[0049] In addition, sodium borate production during the neutralizationof boric acid with sodium carbonate trough reactions (2), (3), and (4),gives the final reaction (5):

Na₂CO₃+4H₃BO₃→Na₂B₄O₇+H₂CO₃+5H₂O,  (2)

H₂CO₃→H₂O+CO₂,  (3)

Na₂B₄O₇+10H₂O→NaB₄O₇*10H₂O, and  (4)

Na₂CO₃+4H₃BO₃+4H₂O→Na₂B₄O₇*10H₂O+CO₂.  (5)

[0050] The neutralization reaction forms the fire-retardant andfungi-resistant compounds making them remain embedded in the insulationmaterial (according previous example: Na2B407*10H2O). It is notnecessary to wash the fibers, thus, low water is consumed and waste isnot generated. Furthermore, due to the slightly slanted slope ofconveyors, excess chemicals drip back into the baths to be reuse.

[0051] The concentration of the boric acid is calculated to produce afull neutralizing reaction, the pH and concentration of this liquorduring the reaction is controlled electronically to have exact amount ofthe reagents. The boric acid is added in the amount of about 8% to about15% of the total weight of the cellulose mixture per times unit of theprocess. The continuous control of the concentration is very importantbecause from the previous processed cellulose mixture was formed asodium borate compounds which serves as seed for the continuousformation of the sodium borate salts, including sodium tetra borate.This is a continuous process calculated on the basis of discrete cyclesat constant velocity of repetition. The fire retardant compounds areprecipitated on the cellulose fiber components as a result of thereaction between the chemicals as they are processed in Bath-II andBath-III. This results in a high level of dispersion of fire-retardantcomponents with strong affinity to the cellulose fiber structure.

[0052] To facilitate the neutralizing reaction, ammonium sulfate isadded at 24% of the cellulose material. This salt serves as a catalystreagent to accelerate the reactions and facilitate the impregnationprocess of the fire retardant compound to the surface of the cellulosefibers. To facilitate the mixing process about 0.01% to about 0.05% ofpalm oil is added to the mixture. Any of these additives act as adeflocculating agent as well as a modifier cross-linking agentconnecting at least two of the cellulose hydroxyl groups to them,generating an improved type of cellulose fiber for insulationproduction. The deactivation of OH cellulose links by using a modifierlimits the further water absorption capacity of the cellulose fibers.The resulting cellulose fibers have increased thermal resistance,durability, and stability and have intrinsic fire-retardant, non-toxic,soundproofing, fungi resistant, and better waterproof properties.Similar properties are not be achieved by using reported methods ofcellulose insulation production or by batting the cellulose carrier rawmaterial with the fire retardant compounds. The produced cellulosematerial in this technological step is strongly controlled.

[0053] Later, the material will be transported (9) into the filter-presssystem (11). Any chemical compound discharged during press dryingprocess is collected and returned to Bath-III.

[0054] A filter-press (11) is used to form a cakes or panels, dependingof the type of the used filter-press. The conformed material istransported on the conveyer (12) to the drier (13). This is a ecologicaltunnel kill calculated to work in any season, geographically situated toreceive the most intense radiation to satisfy high energy efficiency.The architectural roof slope is specially designed for the airflowconvection from the heat zone to the cold zone, where the water isrecuperated by condensation. The solar drier is also provided withelectric heater and ventilators for the clouds days. After the dryingprocess the panels are transported to the packaging department. Thepanels that do not qualify during the quality control are transported tothe hammer mill (14), where they are milled together with the insulationcakes prepared specially for the production of the high disperseinsulation product. At the end, this fine fibrous material is packagedinto bags.

EXAMPLE (Pilot Elaboration)

[0055] 100 Kg of the sugar cane bagasse is milled with the Hammer Millto 15-20 mm particle diameter and washed at 60-Celsius degree into aBath-I strongly agitated for approximately 10 minutes. The amount of thebagasse particles oscillates between 20% and about 25% of the mixture.Later the partially separated cellulose fibers are transported to theBath-II through the conveyer by dripping the remnant sugar and ligninsolution to the Bath-I. The screw of the conveyer continues grinding thefibers and separating the cellulose from the remnant liquor. In Bath-IIthe cellulose fibers are caustic treated using sodium hydroxide solutionprepared at about 5% to about 15% of normal concentration. Subsequently,40 Kg of the recycled cardboard are added to the Bath-II and mixed withthe sugarcane cellulose fibers. The total weight of the cellulosemixture is about 25% of the sodium solution. To facilitate the mixingprocess a about 5% to about 8% of sodium carbonate is added to themixture. After 10 minutes of strongly agitation, the mixture istransported to the Bath-II. From Bath-II to the Bath-III, the velocityof the conveyer and its inclination angle is calculated to carry out anequivalent ratio of cellulose mixture and sodium solution. The measuredratio is approximately 40-60%. The amount of the sodium hydroxide plussodium carbonate impregnated into the cellulose material is about 7% ofthe total cellulose weight.

[0056] Boric acid solution is added to Bath-III for the neutralizationprocess. The neutralization at 40-50 Celsius degree during 15 minutesrequired about 100 liter of boric acid solution at from about 12% toabout 20% of concentration. To facilitate the neutralizing reaction,ammonium sulfate is added at about 2% to about 4% of the cellulosematerial. This salt serves as a catalyst reagent to accelerate thereactions and facilitate the impregnation process of the fire retardantcompound to the surface of the cellulose fibers. To facilitate themixing process about 0.01% to about 0.05% of palm oil is added to themixture. The ammonium sulfate, as well as the palm oil, also serve asstructural modifiers of the cellulose. The produced cellulose materialin this technological step is strongly controlled. The X-ray diffractionanalysis of the inorganic composition of the material show a formationof the family borate compounds, including the sodium tetra borate(Na2B407*10H2O). The microscopic analysis of the dried cellulose fibersprepared in this example shows that borate salts are strongly fixed andwell dispersed on the surface of the fibers, thus the effectiveness ofthe fire-retardant compound is notably higher than the case oftraditionally aspersion of these compounds to the insulation materials.

[0057] The processed material in Bath-III is dried into a filter-pressto form sample of panels. In addition, the conformed and dried materialis pulverized for blowing application. By using the named processes, theproduced insulation material has a bulk density of 29 Kg/m3 (1.81lbs/foot3). The insulation product experimentally produced in accordancewith the invention meets all the applicable government requirements forthe fire resistant material, including those stated in ASTM C-739.

[0058] The present invention involves numerous advantages attainable tothe agricultural byproducts that can be used for the production of fireresistant cellulose material include sugarcane bagasse, guayule bagasse,cellulose-containing farming wastes and by products and other vegetativeresiduals from the extractive processes of oils, resins, wax, andaromatic components.

[0059] The present invention may be embodied in other specific formswithout departing from its spirit or essential characteristics. Thedescribed embodiments are to be considered in all respect only asillustrative and not restrictive and the scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 4. A fire resistant cellulose insulation materialmade from agricultural byproduct containing cellulose fiber, comprisingcellulose fibers that have been bathed in an effective amount of a firstaqueous solution of chemicals suitable for separating and partiallydissolving said cellulose fibers, followed by an effective amount of asecond aqueous solution of chemicals suitable to neutralize said firstaqueous solution, and a fire retardant chemical produced from theneutralization of said first aqueous solution by said second aqueoussolution, said fire retardant chemical precipitated on said partiallydissolved cellulose fibers.
 5. The fire resistant cellulose insulationmaterial of claim 4, wherein said cellulose fibers comprise sugar canebagasse, guayule bagasse, or other cellulose containing farming wastesor mixtures thereof.
 6. The fire resistant cellulose insulation materialof claim 4, wherein said first aqueous solution comprises from about 5%to about 20% weight of sodium hydroxide, sodium carbonate, aluminumhydroxide, sulfuric acid, phosphoric acid or mixtures thereof.
 7. Thefire resistant cellulose insulation material of claim 4, wherein saidsecond aqueous solution comprises from about 5% to about 20% by weightof boric acid, sulfuric acid, aluminum hydroxide, ammonia salts ormixtures thereof.